Metallosupramolecular Polyelectrolytes Self-Assembled from Various Pyridine Ring-Substituted Bisterpyridines and Metal Ions:  Photophysical, Electrochemical, and Electrochromic Properties

This work presents several metallosupramolecular coordination polyelectrolytes (MEPEs) self-assembled from rigid, π-conjugated, pyridine ring functionalized bisterpyridines and metal ions. The MEPEs are water-soluble and display different colors spanning the entire visible regions. Optical, electrochemical, and electrochromic properties of the obtained MEPEs are presented. The results show that the properties are profoundly affected by the nature of the substituents at the peripheral pyridine rings. Namely, MEPEs assembled from the electron-rich OMe group modified ligands exhibit high switching reversibility and stability and show a lower switching potential than the unsubstituted and electron-deficient Br-substituted analogues. The response times can be tuned either by the design of the ligands or by the choice of the metal ions to cover a broad time scale from under 1 s to several minutes. The optical memory is enhanced from 30 s to longer than 15 min as a comparison of unsubstituted and substituted MEPEs shows. Thus, the significantly enhanced stability and the ease of tuning the properties render this type of supramolecular assembly attractive as electrochromic materials for applications in a large variety of areas. Most importantly, we presented the structure−property relationships of MEPEs, which lays the groundwork for further design of new bisterpyridine-based metallosupramolecular functional materials.